This invention relates to the cooling, by air circulation, of outdoor electronic cabinets, and particularly to the cooling of such cabinets by the flow of outside air directly into contact with the electronic components within the cabinet.
In connection with various communication networks, particularly telephone networks, a common practice is to house various electronic components within cabinets disposed at outdoor sites spaced throughout the network. The cabinets stand in the open and provide the sole protection of the electronic components from outside weather conditions.
The electronic components generate heat, and a long standing problem (particularly for cabinets directly exposed to the sun) is the removal of excess cabinet heat. Typically, this is done by air circulation, first by air within the cabinets for conveying heat from heat producing components to a heat exchanger, and second by external air (kept separate from the internal air) past the heat exchanger for the removal of the heat. Originally, self-generated air circulation was sufficient. Then, as the density of components within the cabinets increased, forced air circulation became necessary. Problems now encountered are that large quantities of air must be continuously circulated at relatively high acoustic noise levels and great costs. Also, because the cabinet interior air temperature must be higher than the outside air temperature, for outward direction heat flow, the temperature within the cabinet tracks the outdoor temperature. Typically (although obviously varying from cabinet to cabinet), the cabinet interior temperature is around 19.degree. C. higher than the outside air temperature. However, the higher the temperature of the interior air, the less efficient is the cooling of the components by the circulating air, and heat removal thus requires greater air circulating speeds or higher component temperatures. Either result is undesirable.
It is recognized that greater efficiency of heat transfer would be obtained if the outside air were blown directly against the heat generating components. This would eliminate the aforementioned temperature difference between the inside and outside air temperatures. However, using untreated outside air is out of the question owing to the danger of contamination of the components being cooled. Within large structures, such as telephone network central offices, particularly where people are present, the large cost of treating outside air for use within the structures is both necessary and reasonably cost effective because of the huge volumes of air being treated. For the much smaller outdoor electric cabinets, however, it has long been accepted that the needed treatment of outside air for direct cooling is far too expensive to be practical. Accordingly, the outside cooling air is never admitted into direct contact with the heat generating components. (Some cabinets are vented to the outside area, but only small volumes of air are exchanged, and not for rapid cooling purposes.)
In accordance with the present invention, however, outside air, treated as necessary for avoiding damage to the housed components, is blown directly into contact with the components for increasing the efficiency of heat removal and at reduced cost.